REGULATORY EVALUATION 

NOTICE OF PROPOSED RULEMAKING 

FUEL TANK VENT FIRE PROTECTION 

14 CFR 25 

OFFICE OF AVIATION POLICY AND PLANS 

ECONOMIC ANALYSIS DIVISION 

(APO-300) 

Daniel F. Leach 

April 21, 2014 
2 

I. INTRODUCTION

Current airworthiness standards include requirements (14 CFR 25.981 “Fuel tank ignition 

prevention”) to prevent explosions inside a fuel tank caused by system failures or external 

heating of the fuel tank walls. These requirements do not address explosions caused by externalsource ignition of fuel vapor present in a fuel system vent outlet and the subsequent propagation 

of flame from the vent into the fuel tank. External sources that could cause such ignition include 

lightning, ground handling equipment, or ground fire following a survivable crash landing in 

which the fuel tank and vent system remain intact. 

In this Notice of Public Rulemaking (NPRM) the FAA is proposing an amendment to 14 

CFR 25.975 that would require fuel tank designs with the capability to prevent such fuel tank 

explosions for a minimum of 2 minutes and 30 seconds. 

II. BACKGROUND

The Special Aviation Fire and Explosion Reduction (SAFER) Advisory Committee, 

chartered by the FAA in 1978, found that flame arrestors or suppressors are as effective as 

quenching and suppression systems and supply most of the protection offered by nitrogen 

inerting systems in survivable accidents where minor wing tank damage occurs. Moreover, flame 

arrestors or suppressors were much more practical than the alternative systems. This remains the 

case today. For this proposed rulemaking the FAA is drafting an AC for the use of flame 

arrestors. 

III. ACRONYMS USED IN THIS DOCUMENT 

CFR–Code of Federal Regulations 

FAA–Federal Aviation Administration 

IV. DISCUSSION OF COSTS AND BENEFITS

A. Overview of Costs and Benefits of this Proposed Rule 

The FAA finds the proposed rule to be cost-beneficial because the breakeven expected 

benefits of preventing just two fatalities would outweigh the expected costs ($4.9 million in 

present value benefits versus $4.4 million in present value costs). If this action is not taken, a 

hazard would continue to exist even though effective and low-cost means are available to 

minimize or eliminate it. 
3 

B. Who is Potentially Affected by this Rule?

Manufacturers of newly certified part 25 airplanes and U.S. operators of these airplanes are 

affected by the rule as a result of its applicability to new certification part 25 airplanes. 

Manufacturers and operators of currently produced part 25 airplanes (production cut-in) are 

affected by the rule as a result of its applicability to airplanes engaged in part 121 or 129 

operations produced two years or more after the effective date of this rule. 

C. Principal Assumptions and Sources of Information

 Discount rate is 7 percent (Office of Management & Budget, Circular A-94, “Guidelines and 

Discount Rates for Benefit-Cost Analysis of Federal Programs,” October 29, 1992, p. 8). 

 Value of statistical life (VSL) begins at $9.1 million in 2012, and increases thereafter by an 

annual growth factor of 1.0107. Memorandum: Guidance on Treatment of the Economic 

Value of a Statistical Life in Department Analyses. [February 2013]. United States, Office of 

the Secretary of Transportation. 

 For small part 25 manufacturers: Two U.S. airplane certifications in next 10-year period, 

twenty-one annual U.S. deliveries per U.S. certification; three foreign airplane certifications 

in next 10-year period, eleven annual U.S. deliveries per foreign certification; 15-year 

airplane production run, 30-year retirement age. Internal FAA study.1

 Current airplane models that could be affected by production cut-in requirement (Bombardier 

Dash 8, CJ-700, and CJ-900): FAA 2013 Fleet Forecast, Fleet Forecast Sheet “FAA U.S. 

Airlines 2013-2013 1-18-2103,” “Totals & FAA Tables.” 

 The period of analysis for new certifications is 45 years to account for a complete product 

life cycle determined by a 15-year production period and a 30-year service period. 

 Certification cost estimates for part 25 airplanes—Small U.S. part 25 manufacturers. 

 

1

 We have derived the number of foreign airplane certifications per 10-year period from the source and made a slight 

correction in the figure for U.S. deliveries per foreign airplane certification. 
4 

 Maintenance cost per airplane (every four years) for Bombardier CJ-700/CJ-900 regional jets 

(subject to production cut-in)--$240. As this estimate is for passenger airplane models it is 

much lower than the estimate provided by U.S. manufacturers ($415 annually), which is for 

business jet models. Since business jets are more prone to sit for extended periods of time, 

their flame arrestors can more easily be clogged by ice, mud daubers or other debris, thus 

requiring more frequent and longer maintenance. 

 Minimal fuel costs as flame arrestors weigh between 2 and 4 pounds each. 

D. Costs of this Proposed Rule 

The costs of the proposed rule are engineering, production, and maintenance compliance costs 

for newly certificated part 25 airplanes and for new production of currently produced part 25 

airplanes used in part 121 operations (production cut-in). We first estimate compliances costs for 

new certifications and then for the production cut-in. 

Compliance Cost of New Certifications 

For newly certificated airplanes compliance costs consist of engineering and production costs 

of U.S. manufactured airplanes delivered to U.S. operators and maintenance costs2 of both U.S. 

and foreign airplanes delivered to U.S. operators. U.S. part 25 manufacturers directly incur the 

engineering and production costs while U.S. operators directly incur the maintenance costs. 

Engineering and production costs incurred by foreign manufacturers are not included in the costs 

of compliance, as costs directly attributable to foreign entities are not included in the cost and 

benefit analysis of proposed U.S. regulations. 

To calculate the cost of new U.S. certifications, we assume that all new certifications will be 

approved one year after the effective date of the rule, with production beginning one year later. 

Using an airplane life cycle model, we estimate the economic impact for two new certificates, 

production of 21 airplane/certificates per year, production runs of 15 years and an airplane 

retirement age of 30 years. The costs of new certifications are calculated over an airplane life 

cycle of 45 years (shown in Appendix Table 1). Appendix Table 1 shows 42 deliveries by small 

U.S. part 25 manufacturers annually beginning in 2017 and extending for 15 years through 2031. 

 

2

 As flame arrestors weigh between 2 and 4 pounds each, fuel costs are minimal, so maintenance cost is the only 

operating cost estimated. 
5 

The size of the “New Cert. Operating Fleet” is calculated by adding 33 foreign deliveries to 

the 42 domestic deliveries annually and accumulating through the production cycle. So for 2017, 

the first delivery year, 33 foreign deliveries are added to 42 domestic deliveries resulting in an 

operating fleet of 75. Another 75 airplanes are added in 2018, resulting in an operating fleet of 

150. The new certification operating fleet continues to rise by 75 airplanes annually, peaking at a 

level of 1,125 airplanes at the end of the production run in 2031. The size of the new certification 

operating fleet remains at this peak level until 2047, when it declines by 75, as the first 75 

airplanes delivered in 2017 reach their retirement age of 30 years. The size of the new 

certification operating fleet continues to decline by 75 airplanes a year reaching zero in 2061 

after all airplanes in the fleet have retired. 

Basic cost estimates were solicited from small part 25 manufacturers because large airplane 

manufacturers (Boeing and Airbus) are already compliant with the proposed rule. These cost 

estimates are shown in Table 1 below. 

TABLE 1—INDUSTRY COST ESTIMATES USING FLAME ARRESTORS TO 

COMPLY WITH PROPOSED RULE 

Cost Category Cost Notes 

Nonrecurring Engineering Costs $ 142,000 per model 

Recurring Cost (Hardware & Installation) $ 3,000 

 per model (two flame 

arrestors @ $1,500 each) 

Maintenance Cost (U.S. manufactured airplanes) $ 415 per airplane annually 

Maintenance Cost (Bombardier manufactured airplanes) $ 240 per airplane every 4 years 

The compliance cost estimates consist of nonrecurring (one-time) engineering costs, 

production costs for two flame arrestors per airplane (one per fuel tank) and maintenance costs 

per airplane per year. (The Bombardier maintenance cost estimate will be used later for 

estimating production cut-in costs of compliance.) These three costs are incorporated in a life 

cycle model from airplane design to retirement of the last airplane. As flame arrestors weigh 

between 2 and 4 pounds each, fuel costs are minimal, so maintenance cost is the only operating 

cost estimated. 

These cost estimates are used in the airplane life cycle model introduced above. The assumed 

two new U.S. certifications in the next ten years results in a total engineering costs of $284,000. 
6 

The 42 annual deliveries by small U.S. manufacturers result in $ 3,000 in hardware production 

costs per airplane, for a total of $126,000 annually over the 15-year production period. Annual 

maintenance costs are calculated by multiplying the size of each year’s operating fleet by the 

$415 per airplane maintenance cost. For the 75 airplanes in the new certification operating fleet 

in 2017 the maintenance cost is $31,125. Maintenance cost moves in proportion to the new 

certification operating fleet, rising as the size of the operating fleet increases and falling as the 

size of the operating fleet decreases. 

After the initial nonrecurring engineering costs, annual “Total Cost” in Appendix Table 1 is 

the sum of hardware production costs and maintenance costs. Annual “PV Cost” is the 

discounted value of the annual Total Cost figures, discounting to the beginning of 2014. The 

totals over all years of the airplane cycle are shown in in the top part of Table 2. 

Compliance Costs of Production Cut-In 

In addition to the requirement applying to new certifications, the proposed rule would also 

require a production cut-in for currently produced part 25 airplanes used in part 121 operations.3

To calculate this cost, we first note that the only currently produced and U.S. operated airplane 

models not already in compliance are the Bombardier Dash 8 turboprops and Bombardier CJ700/CJ-900 regional jets. The final rule would apply to these Bombardier models produced 

beginning in 2018. Since the FAA forecasts no future Dash 8 deliveries to U.S. airline operators 

after 2017, we expect no Dash 8 compliance cost for these operators. 

The FAA does forecast the delivery of 338 CRJ-700 and 161 CRJ-900 model airplanes to 

U.S. airline operators over the period 2018-2033. See Appendix Table 4. The engineering and 

production compliance costs for these airplanes are not included in our cost estimates because, as 

noted above, costs directly incurred by foreign entities are not included in the cost and benefit 

analysis of proposed U.S. regulations. Accordingly, for these airplanes we assess the impact on 

U.S. operators only, using Bombardier’s maintenance cost estimate of $240 every four years. 

Allocating this cost as $60 annually and assuming a production period of 16 years, we calculate 

the production cut-in costs for these airplanes as maintenance cost/airplane times the number of 

airplanes over their productive life, using a procedure analogous to that used for new 

 

3

 We do not estimate costs for the analogous part 129 requirement as these costs are directly incurred by foreign 

operators. 
7 

certifications. See Appendix Table 2. We summarize these results in the bottom part of Table 2 

below. 

TABLE 2—COSTS OF NEW CERTIFICATIONS AND COSTS OF 

PRODUCTION CUT-IN 

Cost Categories 

Total 

Undiscounted 

Cost 

PV Cost 

Nonrecurring Engineering Costs $ 284,000 $ 231,829 

Production Costs (Hardware & Installation) $ 1,890,000 $ 936,781 

Operational Costs (Maintenance Costs) $ 14,006,250 $ 3,072,550 

Total Costs for New Certification Airplanes $ 16,180,250 $ 4,241,160 

Maintenance Costs for Production Cut-In 

Airplanes (CRJ-700 & CRJ-900) $ 898,200 $ 178,439 

Total Costs of the Rule $ 17,078,450 $ 4,419,599 

 Note: Details may not sum to totals due to rounding. 

E. Benefits of this Proposed Rule 

 Notwithstanding the absence of post-crash fuel tank explosions in recent years and lacking 

other quantifiable bases upon which to estimate future risks, the merits of the proposed rule can 

be assessed by first noting that nearly all part 25 airplane manufacturers whose airplanes operate 

in the U.S. are already in compliance. Second, we estimate that just two averted fatalities would 

offset the costs of the rule. 

We estimate the breakeven benefits of the rule by estimating the number of averted fatalities 

necessary to offset the $4.4 million present value costs of the rule. After initially finding that one 

averted fatality was not enough to offset the costs of the rule, we found that two averted fatalities 

were sufficient to offset the costs. Our procedure is to first estimate a fatality rate per airplane 

year as the number of averted fatalities divided by the number of airplane years4

 in the airplane 

life cycle = 2/49720 = 0.00004105. The benefits for any year are then equal to this rate times the 

year’s operating fleet multiplied by the VSL for the year.5 (Appendix Table 3 shows that the 

 

4

 The number of airplane years in the airplane life cycle is calculated by summing for each year of the 45-year 

airplane life cycle the number of airplanes in service. 

5

 An Office of the Secretary of Transportation Memorandum estimates of the VSL for 2012 at $9.1 million. The 
8 

VSL increases from $9.6 million for 2017, the first year of production and service, to $15.3 

million in 2061, the last year of the airplane life cycle.) Present value benefits are calculated by 

discounting each year’s benefits by the 7% discount factor for the year. Table 3 summarizes the 

total undiscounted and present value benefits over the airplane life cycle along with the 

undiscounted and present value costs already discussed. 

TABLE 3—TOTAL COSTS AND 

BENEFITS OF PROPOSED RULE 

Undiscounted PV 

Total Costs $ 17.1 $ 4.4 

Total Benefits $ 24.6 $ 4.9 

The FAA finds the proposed rule to be cost-beneficial because the costs of the rule are low 

enough that the expected benefits of preventing just two fatalities would outweigh the expected 

costs. If this action is not taken, a hazard would continue to exist even though effective and lowcost means are available to minimize or eliminate it. As noted previously, large airplane 

manufacturers are already in compliance with the proposed rule, having voluntarily provided the 

level of safety required by the rule.

 Memorandum provides the additional information that the benefits of avoided fatalities should be adjusted annually 

by the growth factor, 1.0107. This adjustment takes into account the effect on VSL of changes in real income over 

time. 
9 

APPENDIX--TABLE 1. COST ESTIMATES FOR NEW CERTIFICATION AIRP

Event/Count Year 

US 

Mfr 

Deliveries Retire- ments 

 Nonrecurring Certiication 

Cost 

Recurring. 

Cost 

(Hardware) 

 Foreign 

Deliveries 

New 

Cert. 

Operating 

Fleet 

 Maintenance 

Cost 

 Tot

Cos

2014 

Effective Date of Rule... 2015 2 Certifications Occur... 2016 284,000 284,0Deliveries Begin... 1 2017 42 126,000 33 75 25,500 151,5

2 2018 42 126,000 33 150 51,000 177,03 2019 42 126,000 33 225 76,500 202,54 2020 42 126,000 33 300 102,000 228,05 2021 42 126,000 33 375 127,500 253,56 2022 42 126,000 33 450 153,000 279,07 2023 42 126,000 33 525 178,500 304,58 2024 42 126,000 33 600 204,000 330,09 2025 42 126,000 33 675 229,500 355,5

10 2026 42 126,000 33 750 255,000 381,011 2027 42 126,000 33 825 280,500 406,512 2028 42 126,000 33 900 306,000 432,013 2029 42 126,000 33 975 331,500 457,514 2030 42 126,000 33 1050 357,000 483,015 2031 42 126,000 33 1125 382,500 508,516 2032 1125 382,500 382,517 2033 1125 382,500 382,518 2034 1125 382,500 382,519 2035 1125 382,500 382,520 2036 1125 382,500 382,521 2037 1125 382,500 382,522 2038 1125 382,500 382,523 2039 1125 382,500 382,524 2040 1125 382,500 382,5

Note: Present values are calculated by discounting to the beginning of 2014, so the discount factor for 2014 is 0
10 

APPENDIX--TABLE 1. COST ESTIMATES FOR NEW CERTIFICATION AIRPLANE

Event/Count Year 

US 

Mfr 

Deliveries Retire- ments 

 Nonrecurring Certiication 

Cost 

Recurring. 

Cost 

(Hardware) 

Foreign 

Deliveries 

New 

Cert. 

Operating 

Fleet 

 Maintenance 

Cost Total Co

25 2041 1125 382,500 382,5026 2042 1125 382,500 382,5027 2043 1125 382,500 382,5028 2044 1125 382,500 382,5029 2045 1125 382,500 382,5030 2046 1125 382,500 382,5031 2047 75 1050 357,000 357,0032 2048 75 975 331,500 331,5033 2049 75 900 306,000 306,0034 2050 75 825 280,500 280,5035 2051 75 750 255,000 255,0036 2052 75 675 229,500 229,5037 2053 75 600 204,000 204,0038 2054 75 525 178,500 178,5039 2055 75 450 153,000 153,0040 2056 75 375 127,500 127,5041 2057 75 300 102,000 102,0042 2058 75 225 76,500 76,5043 2059 75 150 51,000 51,0044 2060 75 75 25,500 25,5045 2061 75 0 0 0 

Total $ 284,000 $ 1,890,000 33,750 $ 14,006,250 $ 16,180,Total ($ mil.) $ 0.3 $ 1.9 $ 14.0 $ 1

Data/Assumptions 

Nonrecurring Certification Cost $142,000 Production Period 15 years Recurring Cost (Hardware)/Airplane $3,000 U.S. Mfr Deliveries/Cert./Year 21 Maintenance Cost/Airplane/Year $415 Foreign Deliveries/Year 33 Discount Rate 7% Airplane Retirement Age 30 years Number of U.S. Certifications (10 years) 2 
11 

 APPENDIX--TABLE 2. COST ESTIMATES FOR BOMBARDIER CRJ-700/900 

 PRODUCTION CUT-IN AIRPLANES 

Year 

CRJ 

US 

Deliveries 

 CRJ 

Retirements 

CRJ 

Operating 

Fleet 

 CRJ 

Maintenance 

Cost 

 CRJ PV 

Maintenance 

Cost Year 

CRJ 

US 

Deliveries 

 CRJ 

Retirements 

CRJ 

Operating 

Fleet 

 CRJ 

Maintenance 

Cost 

 CRJ PV 

Maintenance 

Cost 

2014 2015 2016 2017 2018 34 34 2,040 1,454 2041 499 29,940 4,503 2019 27 61 3,660 2,439 2042 499 29,940 4,208 2020 26 87 5,220 3,251 2043 499 29,940 3,933 2021 21 108 6,480 3,771 2044 499 29,940 3,676 2022 22 130 7,800 4,243 2045 499 29,940 3,435 2023 42 172 10,320 5,246 2046 499 29,940 3,211 2024 37 209 12,540 5,958 2047 499 29,940 3,001 2025 36 245 14,700 6,527 2048 34 465 27,900 2,613 2026 39 284 17,040 7,071 2049 27 438 26,280 2,300 2027 41 325 19,500 7,562 2050 26 412 24,720 2,022 2028 38 363 21,780 7,894 2051 21 391 23,460 1,794 2029 28 391 23,460 7,947 2052 22 369 22,140 1,582 2030 29 420 25,200 7,978 2053 42 327 19,620 1,310 2031 29 449 26,940 7,971 2054 37 290 17,400 1,086 2032 24 473 28,380 7,847 2055 36 254 15,240 889 2033 26 499 29,940 7,737 2056 39 215 12,900 703 2034 499 29,940 7,231 2057 41 174 10,440 532 2035 499 29,940 6,758 2058 38 136 8,160 389 2036 499 29,940 6,316 2059 28 108 6,480 288 2037 499 29,940 5,903 2060 29 79 4,740 197 2038 499 29,940 5,516 2061 29 50 3,000 117 2039 499 29,940 5,156 2062 24 26 1,560 57 2040 499 29,940 4,818 2063 26 0 0 0 

Total 499 499 $898,200 $178,439 
12 

 APPENDIX--TABLE 3. BENEFITS ESTIMATES FOR PROPOSED RULE 

Year 

US New 

Cert. 

Deliveries Retire- ments 

 Foreign 

New Cert. 

Delivies 

Bombardier Pdn 

Cut-In 

Deliveries 

Operating Fleet 

VSL 

Income 

Growth 

Factor 

 VSL 

($ mil.) 

Benefits

($) 

 PV 

Benefits 

($) Year 

Retirements Operat- ing Fleet 

VSL 

Incom

Grow

Facto

2017 42 33 75 1.055 9.6 29,564 22,555 2018 42 33 34 184 1.066 9.7 73,307 52,267 2019 42 33 27 286 1.077 9.8 115,164 76,739 2020 42 33 26 387 1.089 9.9 157,502 98,084 2041 1624 1.362021 42 33 21 483 1.101 10.0 198,675 115,631 2042 1624 1.372022 42 33 22 580 1.112 10.1 241,127 131,157 2043 1624 1.392023 42 33 42 697 1.124 10.2 292,869 148,880 2044 1624 1.402024 42 33 37 809 1.136 10.3 343,567 163,226 2045 1624 1.422025 42 33 36 920 1.148 10.5 394,887 175,335 2046 1624 1.432026 42 33 39 1034 1.161 10.6 448,568 186,140 2047 75 1549 1.452027 42 33 41 1150 1.173 10.7 504,229 195,549 2048 109 1440 1.462028 42 33 38 1263 1.186 10.8 559,700 202,861 2049 102 1338 1.482029 42 33 28 1366 1.198 10.9 611,822 207,245 2050 101 1237 1.492030 42 33 29 1470 1.211 11.0 665,448 210,664 2051 96 1141 1.512031 42 33 29 1574 1.224 11.1 720,151 213,067 2052 97 1044 1.532032 24 1598 1.237 11.3 738,955 204,327 2053 117 927 1.542033 26 1624 1.250 11.4 759,014 196,144 2054 112 815 1.562034 1624 1.264 11.5 767,135 185,273 2055 111 704 1.582035 1624 1.277 11.6 775,343 175,005 2056 114 590 1.592036 1624 1.291 11.7 783,640 165,306 2057 116 474 1.612037 1624 1.305 11.9 792,024 156,145 2058 113 361 1.632038 1624 1.319 12.0 800,499 147,491 2059 103 258 1.642039 1624 1.333 12.1 809,064 139,317 2060 104 154 1.662040 1624 1.347 12.3 817,721 131,596 2061 104 50 1.68

 2062 24 26 1.70

 2063 26 0 1.72

Total 630 495 499 1624 48,720 

Notes: 1. Present values are calculated by discounting to the beginning of 2014, so the discount factor for 2014 is 0.935, etc. 2. Details may no
13 

APPENDIX--TABLE 4. FAA FORECAST OF DELIVERIES OF CJ700/CJ900 AIRPLANES TO U.S A

OPERATORS 

Year 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 

Total

2018-

2033 

CRJ-700 24 17 19 14 15 33 28 29 28 30 27 16 15 17 12 14 338 CRJ-900 10 10 7 7 7 9 9 7 11 11 11 12 14 12 12 12 161 

Source: FAA 2013 Fleet Forecast